Lichess and
chess.com are not in the same "market".
Lichess is a non-profit organization aiming to promote chess and provide a free platform to enjoy this game.
Chess.com is a business organization with profit being the highest the goal.
Lichess.com cannot be bought, because nobody is going to sell it. And while it may have tremendous value, incorporating it into a profitable business will be quite a stretch.
Technically
Chess.com could be bought, but the only reason lichess could consider this is to merge it into its non-profit structure. So it would take lots of donations to then basically turn it upside down.
Be happy about competition, it gives people choices and drives the motivation to make things better.